Process chambers used to deposit film layers using chemical vapor and other deposition techniques can exhaust therefrom materials which must be removed from the exhaust stream to meet environmental and safety regulations. Typically, the exhaust stream is incinerated in a burn box, and in some cases, wet scrubbed, to remove these materials. However, certain compositions or elements cannot be abated by incineration or wet scrubbing. To remove these materials, chemical absorbers are placed in the exhaust stream prior to additional abatement apparatus, to remove some particulates and/or gases from the exhaust stream in point of use applications, where, for example, the exhaust stream is incinerated in a burn box, and optionally wet scrubbed, after passing through the absorber and before entering the house exhaust system. For example, during deposition of group III-V compounds, arsenic and phosphorus are used as a dopant material. These materials cannot be removed from the exhaust stream using incineration or wet scrubbing techniques, and thus an absorber is located in the exhaust piping of the deposition chamber upstream of the burn box and where used, the wet scrubber. The use of compounds such as arsenic-based and phosphorus-based compounds requires use of absorbers in the exhaust path to capture these materials.
The deposition chamber in which the doped III-V thin film is being deposited must be periodically cleaned, using an acidic gas such as HCl. During the cleaning, the HCl is broken down in a plasma and the chlorine is used to remove III-V material which has deposited on the walls of the chamber and the internal chamber components. The etched material is likewise exhausted into the same abatement system used during deposition. Chlorine in the exhaust stream is absorbed in the absorber, significantly reducing the useful life of the absorbing material therein. When the absorber's ability to absorb material declines, the deposition tool has to be shut down, and the absorber material therein replaced, resulting in lost productivity from the deposition tool.
For most substrate processing applications, there is a significant cost associated with both the deposition materials and the exhaust abatement and disposal. The cost of dry absorbers is a big driver in the cost-per-wafer pass for some processes performed in traditional semiconductor fabs. The load of particulates and absorbable gases on dry absorbers increases downtime for cycling the absorbers, and therefore increased cost in the operation of a fab.
Therefore, there is a need for systems and processes that provide for a longer lifetime of the dry absorber.